In medical radiography, x-ray films are used to produce shadow images of patients. When a radiograph is taken the film is positioned between two fluorescent sheets known as intensifying screens and the screens and film are positioned inside a device known as a cassette. The cassette clamps the screens into intimate surface contact with the respective and opposed surfaces of the film. The cassette is light-tight to prevent exposure of the film by ambient light.
In many radiographic studies, a cassette is positioned in a receptor such as a Bucky tray or a spot filmer. Spot filmer and Bucky assemblies are typically equipped with devices known as grids. A grid includes a series of parallel spaced bars of lead or other radiation absorbing material and is positioned between the patient and the film being exposed. The grid permits the passage of primary radiation to produce a shadow image but absorbs so-called scatter radiation which results from refraction of primary radiation. Scatter radiation will, in the absence of the grid, blur the radiographic image.
If a radiograph is to be taken of a patient with a film positioned either in a Bucky or a spot filmer it is necessary first to position the patient on a patient support surface of an x-ray table. There are occasions, such as in a hospital emergency room, when the patient should not be moved for radiographic purposes. For example, it may be very important to determine the extent of an accident victim's injuries before the victim is moved from a stretcher. In that situation, an x-ray technician will simply slide the cassette under a patient and bring an x-ray tube over the patient to take the radiograph.
A prior art portable grid cassette holder for use in an emergency room or the like typically has a grid permanently welded or riveted to a cassette receiving channel. The receiving channel is fixed and will receive only a cassette of a given longitudinal and transverse dimensions and of a specific thickness. Thus the cassette holder will often only be useable with one particular brand of cassette and perhaps only one model.
Most hospitals and clinics have a mixed variety of cassettes on hand. Accordingly, there must be careful matching of cassette and holders to produce good diagnostic results. If there is to be flexibility in which cassettes may be used a significant inventory of cassette holders is needed. Moreover, if it is desired to have a selection of grid bar to space ratios, other grid-channel assemblies have to be stocked to fit each cassette thickness. Inventorying the multitude of holders or grid-channel assemblies required is expensive and their use is time consuming because of the holder-cassette matching required.
An x-ray grid adapter in which adjustable rails are rigidly secured to a grid has been proposed. The rails were to be adjustable to accept cassettes of varying thickness. The operator would take the time, when using such a device, to readjust the rails to receive a new cassette having a different thickness. Also, if it were desired to use a grid having a different ratio, another grid-channel assembly would have to be stocked. When the new grid was used, the rails of the new grid would have to be adjusted to receive the cassette being used.